The present invention pertains to ceramic films and more particularly pertains to a method for patterning metallo-organic precursor film and a method for producing a patterned ceramic film and film products.
Ceramic materials capable of exhibiting specialized properties, such as superconductivity and opto-electrical properties, have great potential in the form of films that are patterned to meet particular needs. The term "film" used herein, is intended to encompass both "thin films", for example, a film 0.1-2 micrometers thick, and "thick films", for example, a film 5-10 micrometers thick.
Conventional semiconductor materials are patterned by a variety of different procedures. One method used in the production of semiconductor layers involves the use of a layer of patterned resist as a stencil to transfer a pattern to an underlying layer. Malwah, M. L. in U.S. Pat. No. 4,398,964 describes such a method in which a thick patterned resist layer is used to block an ion beam and thus transfer a pattern, in a three layer structure. Reichert, U.S. Pat. No. 4,863,556 describes a similar method, in which a pattern is transferred from a photoresist, through an oxide layer to a dielectric layer by ion implantation. The energy of the ion beam and the thickness of the resist layer are such that the ion beam does not completely penetrate through the masking layer or the dielectric layer. The oxide layer, except where damaged by the ion beam, resists etching used to transfer the pattern to the dielectric.
These methods for patterning semiconductor materials, have a shortcoming that the resist layer is thick. Jackel et al in Appl. Phys. Lett. Vol. 39, Aug. 1, 1981, p. 268-270 notes that a thin layer of resist is desirable to reduce forward scatter and backscatter from the electron beam and describes a method, in which a pattern is formed in a thin, outer resist layer and then transferred through a germanium intermediate layer to an inner resist layer, which is used as a stencil for thermal evaporation of gold onto the substrate. The methods used for patterning semiconductor materials are not directly applicable to the patterning of metallo-organic precursor films. The most notable difficulty is interactions between precursor films and conventional resists and resist developers.
A number of methods, have been used for patterning metallo-organic precursors of Ceramic films. Mantese, J. V. et al in Appl. Phys. Lett. Vol. 52, May 16, 1988, p. 1741-1742 describe a method in which a substrate was coated with a 2.6 micron thick layer of metallo-organic precursor, a pattern was exposed in the precursor by means of a broad ion beam, which penetrated through the precursor film in a pattern defined by a stainless steel shadow mask, unexposed precursor was washed away with solvent, and then the remaining exposed precursor was pyrolized and annealed at high temperature to convert the precursor into a patterned ceramic film. Lines as narrow as 10 microns were produced, but the lines were noted as having the shortcoming of very nonuniform widths. Gross, M. E. et al in Appl. Phys. Lett. Vol. 53, Aug. 29, 1988, p. 802-804 describe a similar method, in which nonuniform line widths are not noted, however structures produced were of millimeter dimensions. The shortcomings of these methods, required use of a very accurate shadow mask and either very nonuniform or very large line widths were overcome by Mantese et al, U.S. Pat. No. 4,952,556 by substituting a focused beam for the broad beam and shadow mask. An ion beam, an electron beam and a laser beam were separately used to pattern precursor layers of a thickness of less than 3 to 4.4 micrometers. These focused beam techniques have the shortcomings of much slower processing speed and high capital investment. Another alternative method for the production of patterned ceramic films, which is described in Agostinelli et al U.S. Pat. No. 4,956,335, is a lift-off process in which a precursor layer is deposited over a patterned layer of copper oxide resist. The resist is then removed, leaving precursor in the former openings of the patterned resist layer. This method is subject to the shortcomings of leaving a lift-off layer between the precursor layer and the substrate, which may interact with the precursor layer at elevated temperatures.
It is therefore highly desirable to provide an improved method for patterning precursor film, an improved method for making a patterned ceramic film, and improved film products.
It is also highly desirable to provide an improved method for patterning precursor film, an improved method for making a patterned ceramic film, and improved film products, based upon the utilization of broad beam irradiation without the use of a shadow mask.
It is also highly desirable to provide an improved method for patterning precursor film, an improved method for making a patterned ceramic film, and improved film products, in which destructive interactions of interactive materials can be prevented.
It is also highly desirable to provide an improved method for patterning precursor film, an improved method for making a patterned ceramic film, and improved film products, which utilize a four layer structure on a substrate: precursor film, a protective layer to prevent etching of precursor film, a beam blocking layer, and over the beam blocking layer a resist layer.
It is finally highly desirable to provide an improved method for patterning precursor film, an improved method for making a patterned ceramic film, and improved film products.